Means for preheating turbines



June 23, 1931. E. BROWN MEANS FOR PREHEATING TQRBINES Filed April 26, 1929 0 0-. u OOOOO with the drawings, in which Patented June 23, 1931 UNITED STATES PATENT OFFICE ERIC BROWN, OF BADEN, SWITZERLAND, ASSIGNOR TO A KTIENGESELLSCHAFT BROWN BOVERI 8c CIE., OF BADEN, SWITZERLAND, A JOINT-STOCK COMPANY OF SWITZER- LAND MEANS FOR PREHEATING TURBINES Application filed April 26, 1929, Serial No. 358,208, and in Germany May 3, 1928.

10 and cool uniformly when being put into or taken out of operation and that, during such periods of unequal heating and cooling, the several portions are subjected to stresses which may result in distortion, particularly in the rotating portions thereof. Such distortionwould result in excessive Vibration of the machine which is extremely objectionable, as is well known. Generally, it is necessary to operate a turbine at a very low rate of speed when putting the turbine into operation in order that the several portions thereof may be heated uniformly to avoid the occurrence ofstresses therein before the machine is put into full operation. When the operating temperature of such machines is relatively high, as is the usual practice at the present time, several hours may be required to bring the temperature of a large turbine to such value that the same may be put into full operation.

'30 Another disadvantage of such starting operation of turbines isthat the steam flowing through the turbine in contact with .the relatively cold portions thereof .will condens thereon which further retardsoperation. f

It is accordingly among the objects of the present invention to provide means whereby a turbine may be maintainedin a heated condition therebyfacilitating the starting thereof in an economical manner within a short period of time. v

Another object of the invention is to provide means whereby" either steam or electric heating or a combination of both may 'be utilized to maintain a turbine at substantially the temperature required during operation thereof, V

Objects and advantages, other than those above set forth, will be apparent from the following description taken in consideration Figurel is a diagrammatic representation of a system for maintaining turbines in a heated condition according to the present invention, 7 f

Fig. 2 is a cross-sectional view of one of the heating means to be employed in the system shown in Fig. 1, and

Fig. 3 is aview of a heating means similar to that shown in Fig. 2 but showing a combination of electrical and steam heating, together with means for controlling the supply of energy to the electrically heated element therein.

Referring more particularly to the drawingsby characters of reference, 5 indicates a high pressure turbine of the usual character connected in series with a low pressure tur bine 6, also of the usual type, which is connected to a condenser 7 functioning in the usual manner. A conduit 8 is connected with the usual discharge passage at the exhaust end of low pressure turbine 6 and with a blower 10 driven by a motor 11. The blower 10 is. connected with a heat exchanger 12, by a conduit 13. The heat exchanger is connected with an operating steam inlet and with an operating steam line 16 leading to the high pressure turbine and serves the purposes of a separator for removing water from the turbine operating steam. The heat exchanger 12 is provided with heating means such as a steam heating coil 17 which may be supplied'from the usual boiler (not'shown) supplying the steam for operation of the tur bine or from any other suit-able source. Any condensate collecting in the heat exchanger and water separator is drained therefrom into a trap 18 from which it is discharged to a hot well or boiler (not shown) in the well known manner.

During normal full speed operation of the turbines, a main inlet valve 20 in the operating steam inlet 15 is open, and anozzle control valve 21 in the operating steam connection 16 between heat exchanger 12 and turbine 5 is adjusted in the usualmanner to produce the desired turbine operation. When the turbines are disconnected from the load and are to beretained in heated condition as a standby to carry peak loads, a va1ve'22 in conduit 8 and a valve 23 in conduit 13 are fully opened and main valve 20 is closed. The closing of valve 20 operates a switch 25, connected to the stem of valve 20, which controls the circuit of motor 11. As soon as the motor circuit is closed, the blower connected therewith exhausts the steam remaining in the turbines through the heat exchanger 12 where contact with heating coil 17 again raises the temperature of the steam before it is returned through the turbines. The above described circulation of steam is continued throughout the entire period during which the turbines are to be kept in heated condition. To avoid the possibility that the pressure of the steam might be increased to a dangerous amount, a safety valve 26 is placed in conduit 8 between turbine 6 and blower 11 through which valve the steam may escape if the pressure exceeds that for which the valve is set.

Heat exchanger 12 may be made for steam heating only as is shown in Fig. 2, in which the heating coil 17 is arranged in an annular space between the exterior walls of the heat exchanger and an interior cylinder 27. IVhen the heat exchanger is used to preheat the steam remaining in the turbine, for the purpose of keeping the turbines in heated condition, the steam flows from blower 10 through conduit 13 and passes over the heating coils 17 in the annular space provided therefor in heat exchanger 16 and passes through cylinder 27 into the main steam line. hen the temperature to be maintained is such that it cannot be attained by the use of only the steam heating coil, an electric resistance heating element 28 is arranged within cylinder 27 of heat exchanger. The steam, to be utilized for maintaining the turbine in heated condition, enters the heat exchanger through the conduit 13 and passes over the heating coils 17 and through cylinder 27 where it is superheated by contact with the electric heating element 28 and is discharged from the heat exchanger into the main steam line 16. If, for any reason, the pressure of the steam within the heat exchanger 12 should rise to such value to make it desirable to cut the electric heating element 28 out of circuit, a piston 30 maintained under the pressure of a spring 31 is arranged in an extension 32 of the heat exchanger in communication therewith in such manner that the steam pressure may act on the piston 30 to move the same outwardly against the action of spring 31. The piston is connected to a form of crank 83 which is connected with a bell crank 35 for actuating an electric switch 36 in the circuit supplying the heating element 28. The pressure of the steam acting on the piston 30 forces the same to move outwardly whereby the several cranks take up such position that the electric switch 86 makes or breaks contact in dependence on the steam pressure prevailing in the heat exchanger 12. It will be seen that such arrangement provides an automatic means for maintaining the pressure of the steam circulating through the turbines at an exact predetermined value whereby the temperature of the turbine may be exactly controlled.

It should be clearly understood that the invention has nothing in common with the wellknown drying of turbines and the accompanying condensers, but deals with means for quickly starting a turbine from rest. The temperature ranges for the two operations are entirely different and are brought about by different means. In the invention, the heating fluid is of such temperature that the turbine structure is preheated to and maintained at approximately the operating temperature thereof, whereas, in the usual drying operation, the temperature of the dryin fluid is merely sufficiently high to cause evaporation of any condensate contacting therewith.

Although only one embodiment of the invention has been illustrated and described, it will be understood that various other embodiments are possible, and that various changes may be made without departing from the spirit of the invention or the scope of the claims.

The invention claimed is 1. In a system for retaining turbines at the operating temperature, a turbine, a heat exchanger connected in the steam supply line of the turbine, means connected with said heat exchanger to separate water from the steam supply flowing therethrough, means for supplying said heat exchanger with heat, and means for causing the circulation of heating steam through the turbine and through said heat exchanger.

2. In a system for retaining turbines at the operating temperature, a plurality of turbines, a heat exchanger connected in the steam line of the turbines and serving in normal operation of the turbines as a water separator for the steam supply flowing therethrough, a coil of tubing arranged within said heat exchanger, means for causing flow of heating fluid through said tubing, an electrical heating element within said heat exchanger, means for causing flow of heating current in said element, said coil and said heating element contacting with steam passing therethrough, and means for causing the circulation of heating steam through said heat exchanger and through the turbines.

3. In a system for retaining turbines at the operating temperature, a turbine, a heat exchanger connected in the steam line of the turbine and serving in normal operation of the turbine as a water separator for the steam supply flowing therethrough, a coil of tubing arranged within said heat exchanger and providing a path for the circulation of a heating medium, an electrical heating element within said heat exchanger, said coil and said heating element contacting in series with steam passing through said heat exchanger, and a blower for exhausting steam from the turbine and for forcing the exhausted steam through said heat exchanger for reheating the same.

4. In a system for retaining turbines at the operating temperature thereof, a turbine, a water separating heat exchanger connected with the turbine and forming a portion of the steam supply line therefor, a main valve controlling the flow of operating steam through said heat exchanger, and a blower connected with the turbines and said heat exchanger to force steam through the system to heat the turbine.

5. In a system for retaining turbines at the operating temperature thereof, a plurality of turbines, a water separating heat exchanger connected with the turbine and permitting the supply of operating steam to the turbines therethrough, a main valve controlling the flow of said operating steam through said heat exchanger, a blower connected with the turbines and said heat exchanger to force circulation of steam therethrough to heat said turbines, an electric motor for operating said blower, and a switch controlling the operation of said motor in dependence on the operation of said main valve.

6. In a system for retaining turbines at the operating temperature thereof, a turbine, a water separating heat exchanger connected with the turbine permitting the supply of steam therethrough to operate said turbine, a main valve controlling the flow of said steam through said heat exchanger, a blower connected with the turbine and said heat exchanger to force circulation of steam through the system to heat the said turbine, an electric motor for operating said blower, a switch controlling the operation of said motor in dependence on the operation of said main valve, and an escape valve arranged ad acent the turbine to permit exhausting of the heating steam at pressures above a predetermined value.

In testimony whereof I have hereunto subscribed my name this 12th day of April, A. D. 1929.

ERIC BROWN. 

